VII. ^« Account o/a Singular Halo o/?Af Moon. Com- 

 municated in a Letter from WlLLIAM Hall, Efq; of White- 

 Hall, F. R. S, Edin. to Sir James Hall, Bart. F. R. S^ 

 £din. 



\Read May 2. 1796.] 



Dear Sir James, Whitehall, near Berwick, April 2. 1796. 



ISend under cover the reprefentation of a very fingular Halo 

 of the Moon, (See PI. V.), feen here on the night of the 1 8th 

 of February laft, about i o o'clock, and this I have hitherto delay- 

 ed, in order, if poflible, to gain farther information in the neigh- 

 bourhood concerning it. 



During the fhort contintiance of the fmall halo, which did 

 not exceed 10 mintites after I got notice of it, I could not lay 

 my hands on any other inftrument to take the angles, but a Sis- 

 son's theodolite, which, unluckily, having been conflrudled fo 

 as not to adniit of a vertical angle fo great as the moon's alti- 

 tude then was, I laid it afide, not recoiled in g that it might have 

 meafured feveral of the fmaller angles. But I obferved fundry 

 marks, from which I took the angles as exadly as I could next 

 day. 



The moon was abotit S. W. and her altitude nearly 54°, 

 which of confequence was alfo the akitvide of the limb of the 

 greater halo, where it was higheft, and where it pafled through 



the 



